PROJECT SUMMARY Pancreatic ductal adenocarcinoma (PDAC) is the 4th leading cause of cancer death in the United States with no effective therapy developed to date. With hope to guide the development of precision treatment, recent large scale genetic profilings have established that PDAC is a heterogeneous disease comprised of many distinct molecular subtypes, that correlate with histopathological characteristics and patient outcomes. Among these tumor subtypes, squamous (also called quasi-mesenchymal or basal) subtype exhibit the worst prognosis. However, the underlying mechanisms for the poor survival in this malignant subtype remains largely unknown. Moreover, although oncogenic Kras mutation, the primary driver in PDAC, is universally present in all tumor subtypes, the squamous tumor subtype exhibits diminished reliance on mutant Kras, suggesting additional oncogenic driver dependency which may represent unique vulnerability in this subtype. The long- term goal of my research effort is to systematically explore the molecular underpinnings of PDAC maintenance and to identify context-dependent vulnerabilities as therapeutic targets. Our recent study has revealed selective activation of YAP1 oncogene in squamous subtype tumors. We demonstrated that YAP1 and its partner, TEAD transcription factor, are critical for the growth of squamous subtype tumors. Our current study further identified a TEAD-specific metabolism pathway that is essential for a tumor stem cell-like population that can survive independent of YAP1. Based on our finding, the central hypothesis is that the YAP1/TEAD pathway is the major driver of squamous PDAC subtype that can be therapeutically targeted. To address our hypothesis, we will utilize our novel PDAC mouse models and patient-derived xenograft models to: 1) elucidate the molecular events leading to the activation of YAP/TEAD pathway and tumor growth in squamous subtype of PDAC; 2) determine the mechanisms of TEAD-mediated metabolism reprograming and survival in the stem cell-like population; 3) evaluate the efficacy of combined therapeutic strategy of targeting of YAP and TEAD- dependent metabolism pathway. This grant is significant because a deep understanding of the YAP/TEAD pathway in squamous subtype of PDAC offers important mechanistic insights and strong rationale to target this unique tumor subgroup. It is anticipated that the research is of high translational relevance because our proposed studies will provide strong preclinical evidence for novel combinatory strategies to treat this most lethal form of PDAC.